French Patent FR-A-2,593,081 teaches a central vacuum system composed of a housing comprising at its upper part a compartment accommodating a vacuum system and in its lower part a supply of water, called wash water, whose level touches the opening of a drain line in which a flexible shutoff sleeve valve is mounted controlled by a pressurized water source, and a dip tube immersed in said water supply and connected outside the housing and by a network of fixed pipes to intake openings located in the areas or rooms of a building for residential or other use, the central part of said housing also comprising means for generating the flushing action.
These means are composed of an annular perforated duct located in the central part of the housing, said duct pointing toward the water supply and connected to a pressurized water line that also controls said flexible shutoff sleeve valve.